LED illumination device with a highly uniform illumination pattern

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent document is a continuation-in-part of U.S. application Ser. No. 11/620,968 filed on Jan. 8, 2007, which in turn is a continuation-in-part of U.S. application Ser. No. 11/069,989 filed Mar. 3, 2005, the entire contents of each of which are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention is directed to an LED (light emitting diode) and reflector illumination device that creates a highly uniform illumination/intensity pattern.

Generally, light sources emit light in a spherical pattern. Light emitting diodes (LEDs) are unique in that they emit light into a hemispherical pattern from about −90° to 90° as shown in <figref idref="DRAWINGS">FIG. 1</figref><i>a</i>. Therefore, to utilize an LED as a light source in a conventional manner reflectors are placed around an LED.

<figref idref="DRAWINGS">FIG. 2</figref> shows a background LED illumination device <b>10</b> including an LED <b>1</b> and a reflector <b>11</b>. In the background LED illumination device in <figref idref="DRAWINGS">FIG. 2</figref> the LED <b>1</b> and reflector <b>11</b> are oriented along the same axis <b>12</b>, i.e. along a central optical axis <b>12</b> of the reflector <b>11</b>, and the LED <b>1</b> points directly out of the reflector <b>11</b> along the axis <b>12</b>.

With the LED illumination device <b>10</b> in <figref idref="DRAWINGS">FIG. 2</figref>, wide-angle light is redirected off of the reflector <b>11</b> and narrow angle light directly escapes. The result is that the output of the LED illumination device <b>10</b> is a narrower and more collimated beam of light. Thereby, with such an LED illumination device <b>10</b>, a circular-based illumination pattern is created. Since most LEDs have a Cosine-like intensity pattern as shown in <figref idref="DRAWINGS">FIG. 1</figref><i>a</i>, this results in a hotspot directly in front of the LEDs when illuminating a target surface. The reflector <b>11</b> can increase the illuminance at various area of the target surface but the reflector <b>11</b> cannot reduce the hotspot directly in front of the LED.

SUMMARY OF THE INVENTION

The present inventor recognized that certain applications require highly uniform illumination patterns. In some cases the illumination must not exceed a ratio of 10 to 1 between the highest and lowest illuminance values within the lighted target area. Some examples of this are street lighting, parking garage lighting, and walkway lighting. Applications such as wall-mounted lights require a highly uniform non-circular pattern to direct light at a floor, and not waste light by over illuminating the wall.

As another example of an application in which it would be advantageous to create a non-circular pattern, in certain applications an illumination or intensity distribution may be desired that is broader in one direction than another direction. Automotive lighting applications such as head lamps, turn signals, or tail lamps are examples of such applications. As an example an automotive tail lamp has a desired intensity distribution that is much wider in a horizontal plane than a vertical plane. Such a type of light pattern may be referred to as a long-and-narrow distribution.

Other applications may also benefit from creating a non-circular light output illumination/intensity pattern.

Accordingly, one object of the present invention is to provide a novel LED illumination device that can generate a highly uniform illumination pattern.

A further object of the present invention is to generate a non-circular light output illumination/intensity pattern.

The present invention achieves the above-noted results by providing a novel illumination source including reflectors with a conic or conic-like shape. Further, a light emitting diode (LED) is positioned with respect to a first reflector so that the high intensity light emitted along the central axis of the LED is diverted away from the central axis by the first reflector. A second reflector located opposite the first reflector directs light from a higher angle toward the angle that corresponds to the central axis of the LED. This second reflector essentially fills in light along the central axis of the LED but with a lower intensity that is more appropriate to illuminate the area directly in front of and nearest the LED.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

<figref idref="DRAWINGS">FIGS. 1</figref><i>a </i>and <b>1</b><i>b </i>show the intensity distribution of a conventional LED;

<figref idref="DRAWINGS">FIG. 2</figref> shows a background art LED illumination device;

<figref idref="DRAWINGS">FIGS. 3 and 4</figref> show an LED illumination device according to an embodiment of the present invention;

<figref idref="DRAWINGS">FIG. 5</figref> shows an illumination distribution realized by the LED illumination device of <figref idref="DRAWINGS">FIG. 6</figref><i>a; </i>

<figref idref="DRAWINGS">FIGS. 6</figref><i>a </i>and <b>6</b><i>b </i>show an LED illumination device according to further embodiments of the present invention;

<figref idref="DRAWINGS">FIG. 7</figref><i>a </i>shows a side view and <figref idref="DRAWINGS">FIG. 7</figref><i>b </i>shows an isometric view of an LED illumination device according to a further embodiment of the present invention;

<figref idref="DRAWINGS">FIG. 8</figref> shows an illumination pattern of the LED illumination device of <figref idref="DRAWINGS">FIGS. 7</figref><i>a </i>and <b>7</b><i>b; </i>

<figref idref="DRAWINGS">FIGS. 9 and 10</figref> show an LED illumination device according to further embodiments of the present invention;

<figref idref="DRAWINGS">FIG. 11</figref> shows an LED illumination device according to a further embodiment of the present invention;

<figref idref="DRAWINGS">FIG. 12</figref> shows an LED illumination device according to a further embodiment of the present invention;

<figref idref="DRAWINGS">FIG. 13</figref> shows in a chart form an illumination distribution realized by the LED device of <figref idref="DRAWINGS">FIG. 9</figref>;

<figref idref="DRAWINGS">FIGS. 14</figref><i>a </i>and <b>14</b><i>b </i>show an LED illumination device according to a further embodiment of present invention;

<figref idref="DRAWINGS">FIGS. 15</figref><i>a </i>and <b>15</b><i>b </i>show an LED illumination device according to a further embodiment of the present invention;

<figref idref="DRAWINGS">FIG. 16</figref> shows an LED illumination device according to a further embodiment of the present invention; and

<figref idref="DRAWINGS">FIGS. 17</figref><i>a </i>and <b>17</b><i>b </i>show an implementation of certain embodiments of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to <figref idref="DRAWINGS">FIG. 3</figref> thereof, an embodiment of an LED illumination device <b>90</b> of the present invention is shown. As shown in <figref idref="DRAWINGS">FIG. 3</figref>, an LED illumination device <b>90</b> of the present invention includes the LED light source <b>1</b>, a first reflector <b>15</b>, and a second reflector <b>16</b>.

In one embodiment the LED illumination device of <figref idref="DRAWINGS">FIG. 3</figref> can be used to create a semicircular illumination pattern used for applications such as for a wall-mounted light shown in <figref idref="DRAWINGS">FIG. 4</figref>. In these applications it is desirable to direct the majority of the light forward with only a small amount of light directed backward on the wall. The LED illumination device of <figref idref="DRAWINGS">FIG. 3</figref>, in the configuration and orientation shown, can be inserted into and used in the light fixture shown in <figref idref="DRAWINGS">FIG. 4</figref>.

In the embodiment of the present invention shown in <figref idref="DRAWINGS">FIG. 3</figref>, the reflector <b>15</b> is shaped so that the light emitted directly in front of the LED <b>1</b> (light emitted directly along the central optical axis of the LED <b>1</b>) is redirected away from the central axis of the LED by the reflector <b>15</b>. The light is reflected by reflector <b>15</b> from a positive angle to a dominantly negative angle (<figref idref="DRAWINGS">FIG. 1</figref><i>a </i>shows the positive angle from 0° to 90° and the negative angle from −90° to 0°). The second reflector <b>16</b> is used to fill in the light that would have traveled to the illuminating surface along the central axis of the LED <b>1</b>. With reference to <figref idref="DRAWINGS">FIG. 3</figref>, a portion of the light is redirected by second reflector <b>16</b> from a negative angle to a positive angle.

There is an opening between the two reflectors <b>15</b>, <b>16</b> to illuminate the area on the ground that is not covered by the two reflectors <b>15</b>, <b>16</b>, which may be the target area located between the areas illuminated by the first and second reflectors <b>15</b>, <b>16</b>. Such an orientation creates a light output with a uniform and semicircle based illumination/intensity light pattern suitable for wall-mounting lighting applications, such as shown in <figref idref="DRAWINGS">FIG. 4</figref>.

<figref idref="DRAWINGS">FIG. 1</figref><i>a </i>shows the cosine-like intensity profile of a conventional example LED and <figref idref="DRAWINGS">FIG. 1</figref><i>b </i>shows the illuminance profile that results when an example luminaire with conventional LEDs illuminates a surface directly in front of the LED when no optic is used. In this case the example luminaire includes 52 LEDs each emitting 83 lumens. As shown in <figref idref="DRAWINGS">FIG. 1</figref><i>b</i>, there is a hotspot in the center and the illuminance drops very quickly moving away from the center axis. This is the known cosine-fourth effect. In this example the maximum illuminance is about 21 footcandles and the minimum illuminance is about 0.2 footcandles. The resulting illuminance ratio is over 100 to 1 and would exceed the requirements of most applications.

As noted above with respect to <figref idref="DRAWINGS">FIG. 2</figref>, a background LED illumination device <b>10</b> has the LED <b>1</b> and the reflector <b>11</b> approximately oriented along a same central axis. The result is the generation of a circular-based illumination/intensity pattern. The reflector <b>11</b> can be used to increase the illuminance in various areas of the target surface. However, it is not possible to reduce the illuminance directly in front of the LED using the reflector optic <b>11</b> shown in <figref idref="DRAWINGS">FIG. 2</figref>. In the device of <figref idref="DRAWINGS">FIG. 2</figref> there will always be a hotspot on the illumination surface directly in front of the LED. In that example the illumination does not fall below 21 footcandles. Furthermore, when illuminating an area with a ratio of distance to mounting height as much as 2.5, substantially all of the light within +/−68° is already directed into the target area. <figref idref="DRAWINGS">FIG. 1</figref><i>a </i>shows there is very little light left beyond 68° that can be redirected into the target area with the reflector. This small amount of light cannot significantly increase the low illuminance regions at the edge of the target area.

In contrast to such a background structure such as in <figref idref="DRAWINGS">FIG. 2</figref>, in the embodiment in <figref idref="DRAWINGS">FIG. 3</figref> the surface of the first reflector <b>15</b> crosses directly in front of the central optical axis of the LED <b>1</b>. As a result, the highest intensity light is diverted away from the central axis and toward higher angles. The hotspot is eliminated and this high intensity light is directed toward the edge of the target area where higher intensity light is needed due to the cosine effects.

If only the first reflector <b>15</b> was utilized, a dark area would be left underneath and behind the illumination device <b>90</b>. However, the second reflector <b>16</b> can be used to redirect light emitted from the other side of the LED <b>1</b> to fill in angles obscured by the first reflector <b>15</b>. The light emitted from the side of the LED <b>1</b> is of lower intensity and therefore will not create a hotspot in the center target area located directly in front of the illumination device <b>90</b>. The reflector <b>16</b> can also be shaped to direct a small amount of light backward to appropriately illuminate the wall.

There is an opening between the two reflectors <b>15</b>, <b>16</b> to allow light from the LED <b>1</b> to directly illuminate the region of the target area that is not illuminated by the first and second reflectors <b>15</b>, <b>16</b>. Considering this, the reflector surfaces could also be designed to provide a smooth transition across the target area.

To create the desired light output intensity pattern, the reflectors <b>15</b>, <b>16</b> in the embodiment of <figref idref="DRAWINGS">FIG. 3</figref> can have a conic or conic-like shape. The reflectors <b>15</b>, <b>16</b> can take the shape of any conic including a hyperbole, a parabola, an ellipse, a sphere, or a modified conic.

The reflectors <b>15</b>, <b>16</b> may also be formed of a typical hollowed reflecting surface. If the reflectors <b>15</b>, <b>16</b> are typical hollowed reflecting surfaces, they can be formed of a metal, a metalized surface, or another reflectorized surface.

Further details as to the conic or conic-like shape that the reflectors <b>15</b>, <b>16</b> can take is discussed below.

<figref idref="DRAWINGS">FIG. 6</figref><i>a </i>shows an example of a modification of the embodiment of <figref idref="DRAWINGS">FIGS. 3</figref>, <b>4</b> in which the reflectors <b>15</b>, <b>16</b> in the embodiment of <figref idref="DRAWINGS">FIG. 3</figref> are extruded or projected linearly into reflectors <b>15</b>′, <b>16</b>′ and an array of LEDs <b>1</b> is used.

<figref idref="DRAWINGS">FIG. 5</figref> shows an example of the illuminance profile created by the embodiment of the illumination device of <figref idref="DRAWINGS">FIG. 6</figref><i>a </i>when 52 LEDs each emitting 83 lumens are used. The brightest area has been reduced from about 21 to about 16 footcandles. The light is appropriately directed forward for applications such as wall-mount lights. The illumination gradually decreases out to a ratio of distance to mounting height of 2.5. The least bright region at the edge has increased from about 0.2 footcandles to about 2.6 footcandles. The resulting illuminance ratio is 6 to 1 and would meet the requirements of most applications. With the embodiment of <figref idref="DRAWINGS">FIG. 6</figref><i>a </i>in the invention it would not be difficult to maintain an almost constant illumination out to the edge of the target area, but the intensity at high angles would be very high and may cause objectionable glare.

A cover or lens <b>65</b>, as shown in <figref idref="DRAWINGS">FIG. 6</figref><i>b</i>, can be placed forward of the LED <b>1</b> and reflectors <b>15</b>′, <b>16</b>′ to further modify the illumination/intensity profile. The cover or lens <b>65</b> may spread the light perpendicular to the linear or projected reflector. The cover or lens <b>65</b> could also spread the light in all directions. The cover or lens <b>65</b> could also primarily modify the light not reflected off either of the reflectors.

As a further employment of the embodiment of <figref idref="DRAWINGS">FIGS. 3</figref>, <b>4</b>, when utilizing an array of LEDs <b>1</b>, the reflectors can also be curved or can be completely revolved in a circle as shown in <figref idref="DRAWINGS">FIGS. 7</figref><i>a</i>, <b>7</b><i>b </i>to form a first reflector <b>77</b> (similar to first reflector <b>15</b>) and a second reflector <b>78</b> (similar to second reflector <b>16</b>). <figref idref="DRAWINGS">FIG. 7</figref><i>a </i>shows a side view and <figref idref="DRAWINGS">FIG. 7</figref><i>b </i>shows an isometric view of that further embodiment. Revolving the reflector and using an array of LEDs also creates a highly uniform circular illumination pattern with no hotspot in the center.

An isofootcandle chart for 52 83-lumen LEDs with a revolved reflector of <figref idref="DRAWINGS">FIGS. 7</figref><i>a</i>, <b>7</b><i>b </i>is shown in <figref idref="DRAWINGS">FIG. 8</figref>.

As a modification of the embodiments of <figref idref="DRAWINGS">FIGS. 7</figref><i>a</i>, <b>7</b><i>b</i>, the reflectors can be revolved not only in a circle but can have more complicated curves such as those satisfied by the conic or conic like functions discussed below.

<figref idref="DRAWINGS">FIG. 9</figref> shows an LED illumination device <b>20</b> of another embodiment of the present invention. In the embodiment of the present invention shown in <figref idref="DRAWINGS">FIG. 9</figref>, the LED <b>1</b> is rotated approximately 90°, and preferably 90°±30°, off-axis with respect to the reflector <b>21</b>, i.e. rotated approximately 90° with respect to a central optical axis <b>22</b> of the reflector <b>21</b>. Such an orientation creates an output semicircle based illumination/intensity light pattern.

<figref idref="DRAWINGS">FIG. 10</figref> shows an array of illumination devices <b>20</b> of LEDs and reflectors at 90° with respect to the LEDs. With the configuration in <figref idref="DRAWINGS">FIG. 10</figref>, the LED illumination device therein could also be used in an application such as a wall mounted luminaire as shown in <figref idref="DRAWINGS">FIG. 4</figref>.

As noted above with respect to <figref idref="DRAWINGS">FIGS. 1-2</figref>, a background LED illumination device <b>10</b> has the LED <b>1</b> and the reflector <b>11</b> approximately oriented along a same central axis. The result is generation of a circular-based illumination/intensity pattern.

In contrast to the background structure such as in <figref idref="DRAWINGS">FIG. 2</figref>, in the embodiment in <figref idref="DRAWINGS">FIG. 9</figref> the LED <b>1</b> is rotated at approximately 90°, with respect to the central axis <b>22</b> of the reflector <b>21</b> to create a semicircle-based illumination/intensity pattern.

To create the semicircle-like light output intensity pattern, the reflector <b>21</b> also has a conic or conic-like shape. The reflector <b>21</b> can take the shape of any conic including a hyperbola, a parabola, an ellipse, a sphere, or a modified conic.

The reflector <b>21</b> may be formed of a typical hollowed reflecting surface. If the reflector <b>21</b> is a typical hallowed reflecting surface, it can be formed of a metal, a metalized surface, or another reflectorized surface.

Or, in a further embodiment of the present invention as shown in <figref idref="DRAWINGS">FIG. 11</figref>, an illumination device <b>30</b> can include a reflector <b>31</b> made of a solid glass or plastic material that reflects light through total internal reflection, with the LED <b>1</b> still offset approximately 90° with respect to the central axis <b>32</b> of the reflector <b>31</b>.

In a further embodiment of the present invention as shown in <figref idref="DRAWINGS">FIG. 12</figref>, an illumination device <b>40</b> can include a reflector <b>41</b> with a surface having segmented or faceted conic-reflector surfaces <b>43</b>. That illumination device <b>40</b> still includes an LED <b>1</b> offset approximately 90° with respect to the central axis <b>42</b> of the reflector <b>41</b>.

Choosing the specific shape of any of the reflectors <b>15</b>, <b>16</b>, <b>15</b>′, <b>16</b>′, <b>21</b>, <b>31</b>, <b>41</b>, <b>77</b>, <b>78</b>, <b>79</b> can change the illumination/intensity pattern generated by the LED illumination device <b>20</b>. As noted above, the reflectors <b>15</b>, <b>16</b>, <b>15</b>′, <b>16</b>′, <b>21</b>, <b>31</b>, <b>41</b>, <b>77</b>, <b>78</b>, <b>79</b> each have a conic or conic-like shape to realize a semicircle-based illumination/intensity pattern.

Conic shapes are used commonly in reflectors and are defined by the function:

<maths id="MATH-US-00001" num="00001"><math overflow="scroll"><mtable><mtr><mtd><mrow><mrow><mi>z</mi><mo>=</mo><mfrac><msup><mi>cr</mi><mn>2</mn></msup><mrow><mn>1</mn><mo>+</mo><msqrt><mrow><mn>1</mn><mo>-</mo><mrow><mrow><mo>(</mo><mrow><mn>1</mn><mo>+</mo><mi>k</mi></mrow><mo>)</mo></mrow><mo>⁢</mo><msup><mi>c</mi><mn>2</mn></msup><mo>⁢</mo><msup><mi>r</mi><mn>2</mn></msup></mrow></mrow></msqrt></mrow></mfrac></mrow><mo>⁢</mo><mstyle><mtext></mtext></mstyle><mo>⁢</mo><mrow><msup><mi>r</mi><mn>2</mn></msup><mo>=</mo><mrow><msup><mi>x</mi><mn>2</mn></msup><mo>+</mo><msup><mi>y</mi><mn>2</mn></msup></mrow></mrow></mrow></mtd><mtd><mrow><mo>(</mo><mn>1</mn><mo>)</mo></mrow></mtd></mtr></mtable></math></maths><img file="US7658513B2_D0001.tif" /><br /> where x, y, and z are positions on a typical 3-axis system, k is the conic constant, and c is the curvature. Hyperbolas (k&lt;−1), parabolas (k=−1), ellipses (−1&lt;k&lt;0), spheres (k=0), and oblate spheres (k&gt;0) are all forms of conics. The reflectors <b>11</b>, <b>21</b> shown in <figref idref="DRAWINGS">FIGS. 2 and 9</figref> were created using k=−0.55 and c=0.105. <figref idref="DRAWINGS">FIG. 9</figref> shows the reflector <b>21</b> used in the present embodiments of the present invention. Changing k and c will change the shape of the illumination/intensity pattern. The pattern may thereby sharpen or blur, or may also form more of a donut or ‘U’ shape, as desired.

One can also modify the basic conic shape by using additional mathematical terms. An example is the following polynomial:

<maths id="MATH-US-00002" num="00002"><math overflow="scroll"><mtable><mtr><mtd><mrow><mi>z</mi><mo>=</mo><mrow><mfrac><msup><mi>cr</mi><mn>2</mn></msup><mrow><mn>1</mn><mo>+</mo><msqrt><mrow><mn>1</mn><mo>-</mo><mrow><mrow><mo>(</mo><mrow><mn>1</mn><mo>+</mo><mi>k</mi></mrow><mo>)</mo></mrow><mo>⁢</mo><msup><mi>c</mi><mn>2</mn></msup><mo>⁢</mo><msup><mi>r</mi><mn>2</mn></msup></mrow></mrow></msqrt></mrow></mfrac><mo>+</mo><mi>F</mi></mrow></mrow></mtd><mtd><mrow><mo>(</mo><mn>2</mn><mo>)</mo></mrow></mtd></mtr></mtable></math></maths><img file="US7658513B2_D0002.tif" /><br /> where F is an arbitrary function, and in the case of an asphere F can equal

<maths id="MATH-US-00003" num="00003"><math overflow="scroll"><mrow><mrow><munderover><mo>∑</mo><mrow><mi>n</mi><mo>=</mo><mn>2</mn></mrow><mn>10</mn></munderover><mo>⁢</mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo>⁢</mo><mrow><msub><mi>C</mi><mrow><mn>2</mn><mo>⁢</mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo>⁢</mo><mi>n</mi></mrow></msub><mo>⁢</mo><msup><mi>r</mi><mrow><mn>2</mn><mo>⁢</mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo>⁢</mo><mi>n</mi></mrow></msup></mrow></mrow><mo>,</mo></mrow></math></maths><img file="US7658513B2_D0003.tif" /><br /> in which C is a constant.

Conic shapes can also be reproduced/modified using a set of points and a basic curve such as spline fit, which results in a conic-like shape for the reflectors <b>15</b>, <b>16</b>, <b>15</b>′, <b>16</b>′, <b>21</b>, <b>31</b>, <b>41</b>, <b>77</b>, <b>78</b>, <b>79</b>.

Thereby, one of ordinary skill in the art will recognize that the desired illumination/intensity pattern output by the illumination devices <b>90</b>, <b>20</b>, <b>30</b>, <b>40</b> can be realized by modifications to the shape of the reflector <b>15</b>, <b>16</b>, <b>15</b>′, <b>16</b>′, <b>21</b>, <b>31</b>, <b>41</b>, <b>77</b>, <b>78</b>, <b>79</b> by modifying the above-noted parameters such as in equations (1), (2).

<figref idref="DRAWINGS">FIG. 13</figref> shows an example of an output light semicircle shaped illumination distribution for a wall-mounted light using the illumination device <b>20</b> of <figref idref="DRAWINGS">FIG. 9</figref>. In <figref idref="DRAWINGS">FIG. 13</figref> the line 0.0 represents the wall, <figref idref="DRAWINGS">FIG. 13</figref> showing the illumination distribution with respect to a ratio of floor distance to mounting height. As shown in <figref idref="DRAWINGS">FIG. 13</figref>, a semicircle illumination distribution can be realized by the illumination device <b>20</b> such as in <figref idref="DRAWINGS">FIG. 9</figref> in the present specification, particularly by the reflector <b>21</b> satisfying equation (2) above.

As discussed above, some illumination applications may desire an intensity distribution of output light that is broader in one direction than another. For example, an automotive lighting application such as shown in <figref idref="DRAWINGS">FIGS. 17</figref><i>a </i>and <b>17</b><i>b </i>may desire a light pattern in a long-and-narrow distribution. In the above-discussed embodiments in <figref idref="DRAWINGS">FIGS. 9-12</figref> the shape of the different reflectors <b>21</b>, <b>31</b>, and <b>41</b> can be symmetrical, although non-circular, in the horizontal and vertical axes, and thus those reflectors provide symmetrical non-circular output light intensity distribution. However, by changing the reflecting surfaces of reflectors to have a different curvature in different axes, for example to have a different curvature in the horizontal axis than in the vertical axis, different light intensity distributions can be realized, for example a long-and-narrow light intensity distribution can be output. As shown in <figref idref="DRAWINGS">FIGS. 17</figref><i>a</i>, <b>17</b><i>b </i>in an automotive tail light, in a vertical direction a 20° total light distribution is output, whereas in a horizontal direction a 90° total light distribution is output, and thereby a long-and-narrow light intensity distribution is output.

<figref idref="DRAWINGS">FIGS. 14</figref><i>a </i>and <b>14</b><i>b </i>show a further embodiment of the present invention in which the light intensity distribution is changed in a horizontal axis compared with the vertical axis. <figref idref="DRAWINGS">FIG. 14</figref><i>a </i>shows a side view of an illumination device <b>60</b> according to a further embodiment of the present invention including an LED light source <b>1</b>, a reflector <b>61</b>, and a central optical axis <b>62</b>. <figref idref="DRAWINGS">FIG. 14</figref><i>a </i>shows a vertical axis view of the illumination device <b>60</b>. <figref idref="DRAWINGS">FIG. 14</figref><i>b </i>shows that same reflector <b>60</b> from a top view, and thus shows a horizontal axis view. As shown in <figref idref="DRAWINGS">FIGS. 14</figref><i>a </i>and <b>14</b><i>b </i>the shape of the reflector <b>61</b> in the horizontal axis view as shown in <figref idref="DRAWINGS">FIG. 14</figref><i>b </i>differs compared to the shape of the reflector <b>61</b> in the vertical axis view as shown in <figref idref="DRAWINGS">FIG. 14</figref><i>a</i>. The curvature of the vertical axis and the curvature of the horizontal axis would blend together at radials between the horizontal and vertical axis. Thereby, in the embodiment of <figref idref="DRAWINGS">FIGS. 14</figref><i>a</i>, <b>14</b><i>b </i>two different reflective surface portions are offset from each other by 90°. With such a structure the light output of the illumination device <b>60</b> can have a long-and-narrow distribution that may be useful in certain environments, as a non-limiting example as an automotive tail lamp such as shown in <figref idref="DRAWINGS">FIGS. 18</figref><i>a</i>, <b>18</b><i>b. </i>

Further, in the illumination device <b>60</b> of <figref idref="DRAWINGS">FIGS. 14</figref><i>a </i>and <b>14</b><i>b </i>the shapes of the reflector <b>61</b> are different in both the horizontal and vertical axis, however both shapes still satisfy equations (1) or (2) noted above, and in that case the conic constant k, curvature c, or arbitrary function F would be changed for each reflector portion. Thereby, the reflector <b>60</b> effectively includes first and second reflective portions (in the respective horizontal and vertical axes) that each have a conic or conic-like shape, which differ from each other. Such conic shapes can be reproduced/modified using a set of points in a basic curve such as a spline fit, which results in a conic-like shape for each of the two different reflective portions of the reflector <b>61</b>.

The embodiment noted above in <figref idref="DRAWINGS">FIGS. 14</figref><i>a </i>and <b>14</b><i>b </i>shows a reflector <b>61</b> having essentially two different curvatures, one in a vertical direction as in <figref idref="DRAWINGS">FIG. 6</figref><i>a </i>and one in a horizontal axis as in <figref idref="DRAWINGS">FIG. 14</figref><i>b. </i>

According to a further embodiment of an illumination device of the present invention as shown in <figref idref="DRAWINGS">FIGS. 15</figref><i>a </i>and <b>15</b><i>b</i>, more than two curvatures can be used for a reflector surface.

<figref idref="DRAWINGS">FIGS. 15</figref><i>a </i>and <b>15</b><i>b </i>show respective further illumination devices <b>70</b> and <b>75</b> each including an LED light source <b>1</b> and a central optical axis <b>72</b>. In <figref idref="DRAWINGS">FIG. 15</figref><i>a </i>multiple radially offset curvatures A-G are formed in the reflector <b>71</b> at different radial positions of the reflector <b>71</b>. The different curvatures blend together along the reflector surface. Thereby, a more complicated illumination and intensity profile can be realized.

<figref idref="DRAWINGS">FIG. 15</figref><i>b </i>shows a further illumination device <b>75</b> with a reflector <b>76</b> similar to reflector <b>71</b> in <figref idref="DRAWINGS">FIG. 15</figref><i>a</i>, except that the portions of the curvature of the reflector <b>76</b> have segmented or faceted conic-reflector surfaces, similar to the embodiment in <figref idref="DRAWINGS">FIG. 12</figref>. Although in <figref idref="DRAWINGS">FIG. 12</figref> the reflector is segmented along the curve of the reflector whereas in <figref idref="DRAWINGS">FIG. 15</figref><i>b </i>the reflector is segmented radially. A modified reflector could also combine both types of segmenting from <figref idref="DRAWINGS">FIGS. 12 and 15</figref><i>b. </i>

Also similar to the embodiment of <figref idref="DRAWINGS">FIGS. 14</figref><i>a </i>and <b>14</b><i>b</i>, each different curvature portion A-G of the reflectors <b>71</b>, <b>76</b> in <figref idref="DRAWINGS">FIGS. 15</figref><i>a </i>and <b>15</b><i>b </i>can be reproduced/modified using a set of points and a basic curve such as a spline fit, which results in a conic-like shape for the reflectors <b>71</b>, <b>76</b>. Again, each curvature portion A-G may satisfy equations (1) or (2) noted above, and in that case the conic constant k, curvature c, or arbitrary function F would be changed for each reflector portion.

<figref idref="DRAWINGS">FIG. 16</figref> shows a further embodiment of an illumination device <b>80</b> according to an embodiment of the present invention. That illumination device <b>80</b> of <figref idref="DRAWINGS">FIG. 16</figref> also includes an LED <b>1</b> outputting light to a reflector <b>81</b>, with a similar relationship to an optical axis <b>82</b> as in the previous embodiments. In the illumination device <b>80</b> in <figref idref="DRAWINGS">FIG. 16</figref> the reflector <b>81</b> along one radial positioning has two different areas A and B with different curvatures each of a conic or conic-like shape. That is, each curvature area A and B may also satisfy equations (1) or (2) above, and in that case each curvature portion A and B will satisfy those formulas with a different conic constant k, curvature c, or arbitrary function F. In that case, the conic shapes can also be reproduced/modified using a set of points and a basic curve such as a spline fit, which again results in a conic-like shape for each area A, B of the reflector <b>81</b>.

In each of these further embodiments in <figref idref="DRAWINGS">FIGS. 14-18</figref> noted above a more complicated illumination or intensity distribution output by the illumination devices <b>60</b>, <b>70</b>, <b>75</b>, and <b>80</b> can be realized.

The features in the further embodiments such as in <figref idref="DRAWINGS">FIGS. 12</figref>, <b>14</b><i>a</i>, <b>14</b><i>b</i>, <b>15</b><i>a</i>, <b>15</b><i>b</i>, and <b>16</b> can also be applied to the illumination devices of <figref idref="DRAWINGS">FIGS. 3-7</figref>. That is, those illumination devices in <figref idref="DRAWINGS">FIGS. 3-7</figref> can also include segmented or faceted conic-reflector surfaces <b>43</b> as in <figref idref="DRAWINGS">FIG. 12</figref>, different light intensity distribution in the horizontal axis compared with the vertical axis as in <figref idref="DRAWINGS">FIGS. 14</figref><i>a </i>and <b>14</b><i>b</i>, multiple radially offset curvatures A-G as shown in <figref idref="DRAWINGS">FIGS. 15</figref><i>a </i>and <b>15</b><i>b</i>, and reflecting surface with different areas A, B as shown in <figref idref="DRAWINGS">FIG. 16</figref>.

Obviously, numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.